Preheat Waffle Iron - Preheat your waffle iron according to the manufacturer's instructions. Lightly coat the top and bottom surfaces of the waffle iron with cooking spray, oil, or butter. Place a baking sheet underneath to catch any batter overflow.
Toast Peanuts and Sesame Seeds - In a nonstick skillet over medium heat, toast the chopped peanuts and sesame seeds until golden and fragrant, stirring occasionally, about 4-5 minutes. Remove from heat and let cool.
Whisk Batter - In a mixing bowl, whisk together the Trader Joe's Ube Mochi Pancake and Waffle Mix, egg, milk, and melted butter until batter is smooth and there are no clumps. Fold in the toasted peanuts and sesame seeds and white chocolate chips. - Be careful not to overmix the batter, as this may result in a tough and chewy texture. Also, don't worry if the batter seems a little thick as the mochi in the mix will expand during cooking.
Cook Waffle Cookies - Working in batches, scoop about 2 tablespoons of batter for each cookie onto the waffle iron. Close the lid and cook until the cookies are golden brown and crisp, about 4-5 minutes. Use a fork or spatula to gently remove them from the waffle iron and place them on a parchment-lined baking sheet. - Do not open the waffle iron too early as this may result in the waffle cookie breaking apart. It is also important to let the waffle cookies cool completely before removing them from the waffle iron, as they may break apart if they are still too warm.
Serve and Enjoy - Serve Ube Mochi Pancake Waffle Cookies immediately while still warm, garnished with extra white chocolate chips or sesame seeds if desired. The waffle cookies can also be stored in an airtight container for up to 2-3 days.